JP7601583B2 - How frozen vegetables are produced - Google Patents

Description

The present invention relates to a method for producing frozen vegetables.

Conventionally, frozen vegetables used in frozen prepared foods that can be eaten simply by thawing, such as frozen chinjaoryu (chicken stir-fry) and frozen champon (champon), are preheated by stir-frying, boiling, or other methods before being frozen. Generally, such frozen vegetables have the problem that the desirable texture after heating is reduced during the cold thawing process.

As techniques for suppressing deterioration in texture due to cold thawing of frozen vegetables, there have been disclosed a method for producing frozen foods and beverages selected from the group consisting of frozen cereals, frozen vegetables, frozen fruits, frozen noodles, frozen rice, and frozen pulp drinks, which is characterized by adding 0.2 to 30% (w/w) of α,α-trehalose and then freezing or freeze-drying (Patent Document 1), and a method for producing frozen vegetables, which is characterized by soaking vegetables in a solution containing urea and then freezing them (Patent Document 2).
However, these technologies have their advantages and disadvantages, and there has been a demand for an excellent method for producing frozen vegetables that can suppress the deterioration of texture caused by cold thawing when frozen vegetables are obtained by freezing cooked vegetables.

JP 2001-169766 A JP 2001-224304 A

The present invention aims to provide a method for producing frozen vegetables that can suppress deterioration in texture due to cold thawing of frozen vegetables obtained by freezing heated vegetables.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that by heating vegetables in the presence of a specific emulsifier, the loss of texture of the frozen vegetables obtained by subsequent freezing can be suppressed when thawed in a cold state, and based on this knowledge, they have developed the manufacturing method of the present invention.

That is, the present invention provides a method for producing frozen vegetables, comprising the following steps 1 and 2:
Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester. Step 2: Freezing the vegetables heated in step 1.

The frozen vegetables obtained by the manufacturing method of the present invention have reduced deterioration in texture due to cold thawing.

The vegetables used in the production method of the present invention are not particularly limited, but examples thereof include fruit vegetables, root vegetables, leafy vegetables, stem vegetables, flower vegetables, and sprouted vegetables. Examples of fruit vegetables include eggplant, tomato, bell pepper, chili pepper, shishito pepper, cucumber, pumpkin, pea, green bean, broad bean, corn, and okra. Examples of root vegetables include potato, radish, turnip, carrot, sweet potato, burdock, and taro. Examples of leafy vegetables include cabbage, Chinese cabbage, lettuce, chrysanthemum, spinach, green onion, and Chinese chive. Examples of stem vegetables include asparagus, onion, green onion, garlic, and ginger. Examples of flower vegetables include broccoli, cauliflower, and myoga. Examples of sprouted vegetables include bean sprouts, radish sprouts, and pea sprouts. Among these, germinated vegetables are preferred, and bean sprouts are even more preferred, from the viewpoint of the ease with which the manufacturing method of the present invention can be used.

Before heating, the vegetables used in the manufacturing method of the present invention can be pretreated by washing, removing unnecessary parts, chopping to an appropriate size, etc.

The manufacturing method of the present invention is characterized by carrying out the following steps 1 and 2 using the above-mentioned vegetables.

[Step 1]
Step 1 is a step of heating vegetables in the presence of a polyglycerol condensed ricinoleic acid ester. The polyglycerol condensed ricinoleic acid ester used in step 1 is an esterification product of polyglycerol and condensed ricinoleic acid, and is produced by a known esterification reaction or the like. The polyglycerol is usually a mixture of polyglycerols having different degrees of polymerization obtained by heating glycerol, glycidol, epichlorohydrin, or the like, and subjecting them to a polycondensation reaction. Examples of the polyglycerol include those having an average degree of polymerization of about 2 to 15. Preferably, the average degree of polymerization is about 3 to 10. The condensed ricinoleic acid is a mixture obtained by heating ricinoleic acid and subjecting it to a polycondensation reaction. Examples of the condensed ricinoleic acid include those having an average degree of polymerization of about 2 to 10. Preferably, the average degree of polymerization is about 3 to 6.

The heating method in step 1 is not particularly limited, but examples include stir-frying, baking, boiling, stewing, steaming, and deep-frying. The purpose of the heating is not particularly limited, but examples include cooking heating and blanching (heating for the purpose of deactivating enzymes, sterilizing, etc.), with cooking heating being preferred.

In step 1, the method of heating in the presence of polyglycerol condensed ricinoleate is not particularly limited as long as the polyglycerol condensed ricinoleate is in contact with the vegetables during heating. For example, in the case of stir-frying, an example is a method in which fats and oils in which polyglycerol condensed ricinoleate is dispersed are used as a stir-frying oil to stir-fry the vegetables. For example, in the case of baking, an example is a method in which fats and oils in which polyglycerol condensed ricinoleate is dispersed are evenly mixed with the vegetables and the vegetables are baked in an oven or the like. For example, in the case of boiling, an example is a method in which water mixed with polyglycerol condensed ricinoleate is used as the boiling water to boil the vegetables.

There are no particular limitations on the amount of polyglycerol condensed ricinoleate used during the heating process, so long as it is an amount that can suppress the deterioration of texture due to cooling and thawing of frozen vegetables. For example, when stir-frying or grilling, the amount is usually 0.001 to 2 parts by mass, and preferably 0.005 to 0.5 parts by mass, per 100 parts by mass of vegetables. When boiling, the amount varies depending on the amount of boiling water used, but it cannot be generalized, for example, when boiling vegetables using boiling water in an amount 10 times the mass of the vegetables, the amount is usually 0.01 to 20 parts by mass, and preferably 0.05 to 5 parts by mass, per 100 parts by mass of vegetables.

There are no particular limitations on the heating temperature, but for example, when stir-frying, the product temperature of the vegetables is usually 50 to 100°C, preferably 60 to 90°C. For example, when grilling, the ambient temperature is usually 140 to 240°C, preferably 160 to 200°C. For example, when boiling, the temperature of the boiling water is usually 90 to 100°C, preferably 95 to 100°C.

There is no particular limit to the heating time, but for example, when frying, it is usually 1 to 6 minutes, preferably 2 to 4 minutes. For example, when baking, it is usually 1 to 8 minutes, preferably 2 to 6 minutes. For example, when boiling, it is usually 1 to 8 minutes, preferably 1 to 3 minutes.

The heating is preferably carried out in the presence of tocopherol in addition to polyglycerol condensed ricinoleic acid ester. By heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester and tocopherol, the texture of the frozen vegetables obtained by subsequent freezing is further suppressed from deteriorating due to cold thawing.

The above-mentioned tocopherols are not particularly limited as long as they are those that are commonly used in foods, but examples include dl-α-tocopherol (food additive), d-α-tocopherol (food additive), d-γ-tocopherol (food additive), d-δ-tocopherol (food additive), mixed tocopherols (food additive), etc.

Examples of the mixed tocopherols include tocopherols recovered from deodorized distillates (e.g., deodorized scum, deodorized sludge, hotwell oil, etc.) that are by-produced in the process of refining vegetable oils. Specific examples include d-α-, d-β-, d-γ-, and d-δ-tocopherols obtained by separating and refining deodorized distillates of canola oil, sesame oil, rice bran oil, safflower oil, soybean oil, corn oil, rapeseed oil, palm oil, sunflower oil, cottonseed oil, peanut oil, etc., and mixtures containing d-α-, d-β-, d-γ-, and d-δ-tocotrienols, which are homologues of tocopherol, etc.

The method of carrying out the above heating in the presence of polyglycerol condensed ricinoleate and tocopherol is not particularly limited as long as the polyglycerol condensed ricinoleate and tocopherol are in contact with the vegetables during heating. For example, in the case of stir-frying, a method of stir-frying the vegetables using fats and oils in which polyglycerol condensed ricinoleate and tocopherol are dispersed as a stir-frying oil can be mentioned. For example, in the case of baking, a method of uniformly coating the vegetables with fats and oils in which polyglycerol condensed ricinoleate and tocopherol are dispersed and baking the vegetables in an oven or the like can be mentioned. For example, in the case of boiling, a method of boiling the vegetables using water in which polyglycerol condensed ricinoleate and tocopherol are mixed as a boiling water can be mentioned.

When the heating is carried out in the presence of polyglycerol condensed ricinoleic acid ester and tocopherol, the amount of tocopherol used is not particularly limited as long as it is an amount that can suppress the deterioration of texture due to cooling and thawing of frozen vegetables. For example, when stir-frying or grilling, the amount is usually 0.0002 to 0.4 parts by mass, preferably 0.001 to 0.1 parts by mass, per 100 parts by mass of vegetables. When boiling, the amount varies depending on the amount of boiling water used, but for example, when boiling using boiling water in an amount 10 times the mass of the vegetables, the amount is usually 0.002 to 4 parts by mass, preferably 0.01 to 1 part by mass, per 100 parts by mass of vegetables.

[Step 2]
Step 2 is a step of freezing the vegetables heated in step 1. In step 2, the freezing conditions are not particularly limited as long as they are general freezing conditions for vegetables, and the freezing temperature is, for example, usually −50 to −5° C., and preferably −35 to −25° C. Freezing methods include, for example, slow freezing and quick freezing, and quick freezing is preferred from the viewpoint of suppressing deterioration in texture due to cold thawing of frozen vegetables.

The manufacturing method of the present invention may include any step other than steps 1 and 2. For example, an optional step performed between steps 1 and 2 may include a step of cooling the vegetables heated in step 1.

The method for thawing the frozen vegetables obtained by the production method of the present invention may be any method commonly used for thawing frozen vegetables, such as natural thawing at room temperature, thawing in a refrigerator, thawing in a microwave oven, thawing in running water or in a hot water bath, etc.

The manufacturing method of the present invention can be preferably implemented when manufacturing frozen prepared foods using vegetables as raw materials. There are no particular limitations on the prepared foods, but examples include chinjaorousu (fried pork with green peppers), champon (champon), tanmen (fried noodles with noodles), hikororo (fried pork with vegetables), mapo tofu (fried vegetables with vegetables), and stir-fried vegetables.

The manufacturing method of the present invention will be described below in the form of examples, but these are merely for the purpose of explaining the manufacturing method of the present invention and are not intended to limit the manufacturing method of the present invention.

[Production of frozen fried bean sprouts]
(1) Production Example 1
10 g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.) and 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were mixed to prepare a stir-frying oil. The stir-frying oil was heated in a frying pan, 200 g of bean sprouts were added thereto, and the bean sprouts were stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the stir-frying oil was evenly mixed with the bean sprouts. Then, 2.4 g of salt was added and the bean sprouts were stir-fried for another minute. Next, the stir-fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen stir-fried bean sprouts (Example Product 1).

(2) Production Example 2
Frozen stir-fried bean sprouts (Example 2) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.05 g.

(3) Production Example 3
Frozen stir-fried bean sprouts (Example 3) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.25 g.

(4) Production Example 4
Frozen stir-fried bean sprouts (Example 4) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 0.5 g.

(5) Production Example 5
Frozen stir-fried bean sprouts (Example 5) were obtained in the same manner as in Production Example 1, except that the amount of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) used was changed to 1 g.

(6) Production Example 6
10 g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.), 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.), and 0.02 g of tocopherol (trade name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) were mixed to prepare a stir-frying oil. The stir-frying oil was heated in a frying pan, 200 g of bean sprouts were added thereto, and the mixture was stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the stir-frying oil was uniformly mixed with the bean sprouts. Then, 2.4 g of salt was added, and the mixture was further stir-fried at a product temperature of 75°C for 1 minute. Next, the stir-fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen stir-fried bean sprouts (Example Product 6).

(7) Production Example 7
The same process as in Production Example 1 was repeated, except that 1 g of propylene glycol fatty acid ester (product name: Rikemal PS-100; manufactured by Riken Vitamin Co., Ltd.) was used instead of 0.1 g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.), to obtain frozen stir-fried bean sprouts (Comparative Example 1).

(8) Production Example 8
10g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.) was heated in a frying pan, 200g of bean sprouts were added thereto, and the mixture was stir-fried at a product temperature of 75°C for 2 minutes and 30 seconds while stirring with a spatula so that the rapeseed oil was evenly mixed with the bean sprouts, after which 2.4g of salt was added and the mixture was further stirred for 1 minute to obtain fried bean sprouts. Next, 0.1g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was added to the fried bean sprouts and mixed evenly. Next, the fried bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen fried bean sprouts (comparative example 2).

(9) Production Example 9
Frozen stir-fried bean sprouts (Control Product 1) were obtained in the same manner as in Production Example 1, except that 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[Evaluation of texture of frozen stir-fried bean sprouts after thawing]
The resulting frozen stir-fried bean sprouts (Example products 1 to 6, Comparative examples 1 and 2, and Control product 1) were thawed by heating in a microwave oven at 700 W for 1 minute 30 seconds, and then eaten, and a sensory evaluation test was conducted. In the test, evaluation was carried out by 10 panelists according to the evaluation criteria shown in Table 1, and the average evaluation points were calculated and coded according to the following criteria. The results are shown in Table 2.
◎: Average score 3.5 or more ◯: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

As is clear from the results, the frozen stir-fried bean sprouts obtained using the manufacturing method of the present invention (Example products 1 to 6) were excellent, with results of "good" or better. In contrast, the frozen stir-fried bean sprouts obtained using the manufacturing method of the comparative example (Comparative example products 1 and 2) were rated "good" and inferior to those obtained using the manufacturing method of the present invention.

[Production of frozen roasted bean sprouts]
(1) Production Example 10
9.9 g of rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.) and 0.1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were mixed, and the mixture was added to 200 g of bean sprouts and mixed uniformly. The bean sprouts were baked for 4 minutes at an internal temperature of 180°C using a steam convection oven (model: SCC WE101; manufactured by Rational Japan Co., Ltd.). Next, the baked bean sprouts were frozen for 60 minutes at -30°C using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen baked bean sprouts (Example Product 7).

(2) Production Example 11
Rapeseed oil (trade name: rapeseed salad oil; manufactured by Boso Oil & Fat Co., Ltd.) 9.88 g, polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) 0.1 g, and tocopherol (trade name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) 0.02 g were mixed, and the mixture was added to 200 g of bean sprouts and mixed uniformly. The bean sprouts were baked for 4 minutes at an internal temperature of 180°C using a steam convection oven (model: SCC WE101; manufactured by Rational Japan Co., Ltd.). Next, the baked bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen baked bean sprouts (Example Product 8).

(3) Production Example 12
Frozen roasted bean sprouts (Control Product 2) were obtained in the same manner as in Production Example 10, except that 0.1 g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[Evaluation of texture of frozen roasted bean sprouts after thawing]
The resulting frozen roasted bean sprouts (Examples 7 and 8, and Control 2) were thawed in a microwave oven at 700 W for 1 minute 30 seconds and then eaten, and a sensory evaluation test was conducted. In the test, 10 panelists evaluated the bean sprouts according to the evaluation criteria shown in Table 3, and the average score was calculated and coded according to the following criteria. The results are shown in Table 4.
◎: Average score 3.5 or more ◯: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

As is clear from the results, the frozen roasted bean sprouts obtained using the manufacturing method of the present invention (Examples 7 and 8) achieved excellent results, rated as "good" or better.

[Production of frozen boiled bean sprouts]
(1) Production Example 13
2000 g of water and 1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) were placed in a pot, stirred for 30 seconds, and heated to boiling. 200 g of bean sprouts were then added and boiled for 2 minutes while stirring. The boiled bean sprouts were then frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen boiled bean sprouts (Example Product 9).

(2) Production Example 14
2000 g of water, 1 g of polyglycerol condensed ricinoleic acid ester (trade name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.), and 0.2 g of tocopherol (trade name: Riken E Oil 700; manufactured by Riken Vitamin Co., Ltd.) were added to a pot, stirred for 30 seconds, and heated to boiling. Then, 200 g of bean sprouts were added and boiled for 2 minutes while stirring. Next, the boiled bean sprouts were frozen at -30°C for 60 minutes using a quick freezer (model: 253FFB; manufactured by Yamato Reiki Kogyo Co., Ltd.) to obtain frozen boiled bean sprouts (Example Product 10).

(3) Production Example 15
Frozen boiled bean sprouts (Control Product 3) were obtained in the same manner as in Production Example 13, except that 1 g of polyglycerol condensed ricinoleic acid ester (product name: Poem PR-300; manufactured by Riken Vitamin Co., Ltd.) was not used.

[Evaluation of the texture of frozen boiled bean sprouts after thawing]
The resulting frozen boiled bean sprouts (Examples 9 and 10, and Control 3) were thawed in a microwave oven at 700 W for 1 minute 30 seconds, and then eaten and subjected to a sensory evaluation test. In the test, evaluation was carried out by 10 panelists according to the evaluation criteria shown in Table 5, and the average score was calculated and coded according to the following criteria. The results are shown in Table 6.
◎: Average score 3.5 or more ◯: Average score 2.5 or more, less than 3.5 △: Average score 1.5 or more, less than 2.5 ×: Average score less than 1.5

As is clear from the results, the frozen boiled bean sprouts obtained by the manufacturing method of the present invention (Examples 9 and 10) achieved excellent results of "good" or better.

Claims (2)

A method for suppressing deterioration in texture of frozen vegetables due to cold thawing , comprising carrying out the following steps 1 and 2:
Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleic acid ester. Step 2: Freezing the vegetables heated in step 1. A method for producing frozen vegetables, comprising the following steps 1 and 2:
Step 1: Heating vegetables in the presence of polyglycerol condensed ricinoleate and tocopherol
Step 2: Freezing the vegetables cooked in step 1